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Torii, Tatsuo*; Sasaki, Miyuki; Sanada, Yukihisa
Proceedings of 2023 IEEE Nuclear Science Symposium, Medical Imaging Conference and International Symposium on Room-Temperature Semiconductor Detectors (IEEE NSS MIC RTSD 2023) (Internet), P. 1, 2023/11
Radiation imaging is useful in various fields where the location of radiation sources needs to be identified. Especially in environments where radiation sources are distributed in three dimensions and difficult to locate, the development of a small imaging sensor that can detect radiation in the 4-
direction will have a significant impact on the progress of work. We have developed a radiation detector with a fractal geometry. This is a unit of tetrahedral radiation sensors, 16 sensors are arranged in a Sierpinski tetrahedron shape, and the space between the sensors is filled with heavy metals. The count rates of the individual sensors make it possible to determine the direction of radiation incidence. Furthermore, since there is no external shielding, the distribution of charged particles, such as beta rays, can also be measured. We have analyzed the response of the Sierpinski radiation detector with respect to the incident direction of gamma and beta rays and compared it with experimental results to understand the sensitivity characteristics.
Morishita, Yuki; Higuchi, Mikio*; Kaneko, Junichi*; Kitagawa, Yuichi*; Akedo, Jun*; Soma, Mitsugu*; Matsui, Hiroaki*
no journal, ,
This paper describes the development of a large-area imaging detector capable of measuring the detailed distribution of alpha particles on hands and feet for use in entry/exit control monitors in decommissioning sites such as the Fukushima Daiichi Nuclear Power Plant. The detector was developed using a commercially available ZnS(Ag) scintillator and an electron multiplying CCD camera. The effectiveness of the detector was evaluated by measuring several types of radiation sources, and the results showed that it was possible to detect the position of alpha particles in a very short time, and contamination levels of up to 11 Bq/cm
could be visualized. The field of view of the detector was also checked, and it was confirmed that the setup had a field of view that could cover most of the hand and the sole of the shoe. This detector is expected to be useful for preventing internal uptake and decontamination.
Morishita, Yuki; Kitayama, Yoshiharu
no journal, ,
The paper discusses the development of a phoswich detector that can discriminate between alpha, beta, and gamma radiation using pulse shape discrimination technology. The detector has two layers of scintillators, a stilbene scintillator for detecting alpha and beta particles and a GAGG scintillator for detecting gamma rays. The study aims to apply machine learning techniques to radiation measurement using data from the phoswich detector. The K-nearest neighbors algorithm was used to classify the different types of radiation. The results showed that increasing the number of neighbors improved accuracy, and a value of 20 was chosen for radiation classification. The study demonstrates the effectiveness of machine learning in efficient and automatic alpha/beta/gamma ray discrimination and radionuclide identification, which can help workers with little experience in radiation to work in the field.
field of view gamma-ray imaging methodKitayama, Yoshiharu; Nogami, Mitsuhiro*; Hitomi, Keitaro*
no journal, ,
To, Kentaro; Nakamura, Tatsuya; Sakasai, Kaoru; Yamagishi, Hideshi*
no journal, ,
Optical signal transmission devices were developed for a two-dimensional neutron detector system. The devices are used for long-distance signal transmission between the detector head installed in the measurement room and the data acquisition equipment installed in the data acquisition room. The developed devices were tested using detector-simulating signals, double pulses of various time intervals, and continuous pulses of various frequencies. The results showed that the devices can transmit two-dimensional neutron data with a counting rate linearity of more than 1.3 MHz and a pulse-pair resolution of less than 0.4 microseconds. Using optical fiber for signal transmission is advantageous due to its compactness, light weight, low transmission loss, and immunity to electrical noise. These features make it suitable for long-distance signal transmission in large-scale experimental facilities.
Watanabe, Kenichi*; Hitomi, Keitaro*; Nogami, Mitsuhiro*; Maeda, Shigetaka; Onabe, Hideaki*
no journal, ,
Thallium bromide (TlBr) is a compound semiconductor attractive for gamma-ray spectrometers. TlBr detectors have shown excellent energy resolution, however, these results were obtained from relatively small crystal detectors. The next phase of TlBr development is to increase the detector size and improve the yield rate of detector production. So far, we have evaluated crystal quality of TlBr by using the neutron Bragg-dip imaging, which is one of the neutron diffraction techniques. In this study, we prepared a large TlBr crystal wafer with a diameter and thickness of 50 mm and 12 mm, respectively. We evaluated the quality of the large crystal by the neutron Bragg-dip imaging. The center region of the large TlBr crystal confirmed to be uniform and well-aligned. As a future work, we will evaluate the electric properties, such as the mobility-lifetime product, at various positions in this large crystal.
Komeda, Masao; Tanabe, Kosuke*; Toh, Yosuke
no journal, ,
Morishita, Yuki; Sagawa, Naoki; Fujisawa, Makoto; Kurosawa, Shunsuke*; Sasano, Makoto*; Hayashi, Masateru*; Tanaka, Hiroki*
no journal, ,
This study reports the effects of different types of radiation on a high-resolution alpha imager, developed using an Electron Multiplying Charge-Coupled Device (EMCCD) camera. The imager was originally designed to visualize Pu oxide particles in decommissioning sites, where other types of radiation such as beta particles, gamma-rays, and neutrons are also present. The study aims to confirm the effects of these radiations on the imager and to develop a discrimination method between alpha particles and other radiations. The measurement of alpha particles, beta particles, gamma-rays, and neutrons were performed. The discrimination method was based on the characteristics of the image distribution, where the image values were binarized and a Gaussian filter was applied to count the number of alpha particle spots. The results show that it is possible to discriminate between alpha and gamma (neutron) rays using the difference in intensity. The study provides important information for the development of radiation detection techniques in decommissioning sites.
Nakamura, Tatsuya; To, Kentaro; Kiyanagi, Ryoji; Ohara, Takashi; Hosoya, Takaaki; Tobe, Masahiro; Hishinuma, Yukio*; Ebine, Masumi; Sakasai, Kaoru
no journal, ,
New detector modules have been developed based on a 
Li:ZnS scintillator and wavelength-shifting fibers technology to upgrade the detectors for SENJU neuron diffractometer at J-PARC MLF. The detector upgrade plan includes (1) Thin-type add-in detectors, (2) High efficiency detectors to replace the original ones, (3) a large area detector for installation under the sample vacuum tank (Large area bottom detector), and (4) One detector-bank detectors. As for (1) and (2) the detector modules have been developed with a 1.5-fold improved detection efficiency with a 50-60% smaller detector depth. 4 add-in detectors and 6 replacement detectors have been manufactured and installed to the diffractometer. The large area bottom detector that has a four-fold larger neutron-sensitive area than the original detector, has also been developed. To increase the light collection efficiency a scintillation light is collected from the both ends of the wavelength-shifting fiber. The prototype detector exhibited an acceptable count uniformity 5
9% over the detector.
